Yam Plant Growth and Tuber Yield Response to Ex-Situ Mulches of Moringa Oleifera, Chromolaena Odorata and Panicum Maximum Under Three Natural Fallow Aged Systems

A field study was conducted at Atonsu, Sekyere Central District of the Ashanti region in Ghana from 2013 to 2014, to(i) determine the effects of ex-situ mulches of Moringa oleifera, Chromolaena odorata and Panicum maximum on yam tuber yield under three natural fallow aged systems and (ii) assess the changes in the physico- chemical properties of the soil with the application of the ex-situ mulches. The field experiment was laid out in a 3x3 factorial arrangement in a Randomized Complete Block Design (RCBD) with three replications. The first factor was ex-situ mulch types at three levels; Panicum maximum (farmers’choice), Chromolaena odorata and Moringa oleifera. The second factor was natural fallow aged systems at three levels; 3-year old, 5-year old and 7- year old. Data collected included changes in soil physico-chemical properties, residue decomposition and nutrient release patterns, yam growth parameters and total tuber yield of yam. After two years of mulch application and cropping, there were significant increases in soil pH, nitrogen, organic matter, calcium and E.C.E.C levels for all the three mulches in comparison to their initial contents. In spite of this, soils under Moringaoleifera mulch recorded significantly higher contents of total nitrogen and organic matter than under the Panicum maximum and Chromolaena odorata mulches Furthermore, M. oleifera produced significantly the highest tuber yields. In terms of yield sustainability over the two years cropping period, there was less yield decline arising from the application of the M. oleifera mulch (19.17%) than from C. odorata (31.53%) and P. maximum (48.20%) mulch applications. The study concluded that M. oleifera mulch was better able to improve and sustain soil fertility which subsequently resulted in higher yam tuber yields than the other mulches of C. odorata and P. maximum. Furthermore, yield reductions in yam was least under M. oleifera mulch and therefore could be considered as the best candidate to ensure sustainable yields of yam on the same piece of land for longer cropping periods.

Keywords: Soil physico-chemical properties, yam growth, soil nutrients, tuber yield.